After the death of her husband, Rieko raised her son Kousuke single-handedly. As Kousuke grows up, he begins to harbor evil feelings toward her mother from his sexual awakening. But even though she was aware of it, she pretended not to see her. And on the night before his marriage, Rieko said to Kousuke, who could only release herself by masturbating, "Tonight is the last night we'll spend together as a parent and child..." and gave her mother and child sex education for the last time. However, her irrepressible desire drives them to further forbidden acts...
